<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        table,td{
            border: 3px solid green;

        }

        table{
            border-collapse:collapse ;  /*单边框*/
            width: 500px;
            height: 300px;
            
        }
        td{
            text-align: center;
            vertical-align: top;
            padding: 20px;
            background-color: gold
        }
    </style>
</head>
<body>
    <table >
        <tr>
            <td>单元格</td>
            <td>单元格</td>
            <td>单元格</td>
        </tr>
        <tr>
            <td>单元格</td>
            <td>单元格</td>
            <td>单元格</td>
        </tr>
        <tr>
            <td>单元格</td>
            <td>单元格</td>
            <td>单元格</td>
        </tr>
    </table>
</body>
</html>